Question on fill above deck footings

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J

joshl

Member
Jun 9, 2021
21
Wisconsin
See photo below. We just installed a prefabricated deck, and the top of the back footings ended up a few inches below grade. I'm wondering what would be an appropriate backfill. I'd want to keep access to the footing brackets if needed in the future, so maybe lay fabric over than backfill with stone...or do I need more to prevent water from getting down there?

(Note that I couldn't install the footing higher up, since the posts are not meant to be cut, but instead lowered into the ground until the deck is the proper height above the pool)

Thanks in advance!

20220625_114559.jpg
 
How about a circle of fake grass, or some river rocks? River rocks are often used for outdoor decor, their smooth, not too big and would hold that space covered well. Usually found in the outdoor pond or landscaping area of hardware stores.
River Rock

Maddie ☮️
 
joshl said:
Note that I couldn't install the footing higher up, since the posts are not meant to be cut
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Why not (according to what)?

The top surface of a footing is meant to be above grade. Well above grade. Period. There is nothing you're going to be able to fabricate to keep that assebly dry or keep it from rusting or corroding (the post or the brackets or those concrete screws). Any type of rock will eventually fill with debris (dirt, dust, salt, leaves, grass clippings, etc) and become the perfect moisture retainer. Cutting the post and raising the footing with concrete is the correct solution (unless there is some reason I cannot fathom not to cut the post).
 
Dirk said:
Why not (according to what)?

The top surface of a footing is meant to be above grade. Well above grade. Period. There is nothing you're going to be able to fabricate to keep that assebly dry or keep it from rusting or corroding (the post or the brackets or those concrete screws). Any type of rock will eventually fill with debris (dirt, dust, salt, leaves, grass clippings, etc) and become the perfect moisture retainer. Cutting the post and raising the footing with concrete is the correct solution (unless there is some reason I cannot fathom not to cut the post).
Click to expand...
It's a prefabricated steel/resin deck. It was completely built, then set in place, as opposed to building from the ground up. The instructions specifically say to not cut the posts, but instead bury below ground until you have the proper deck height. The instructions also say to just set the posts on concrete block, but the city inspector required attaching to concrete footings. The posts are 4x4 wood encased in resin. Not sure how well they would cut, but wouldn't want to take the chance anyway.

Link to the instructions: http://www.vinylworkscanada.com/wp-content/uploads/2014/07/Model-FD-Installation-Instructions.pdf

Not disagreeing with you though. You're probably right about eventually corroding, etc.
 
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OK, understood. Tough call. Hopefully the resin will do its job for a good, long while. If it were me, and it wasn't too late, I would remove the brackets and slather the inside with 100% silicone caulk, especially around the screw holes, and then cover the screw heads with silicon, too, after you reassemble. Those penetrations are where the corrosion will start. Additionally, the "sandwich" created by the bracket and post will retain moisture and that will accelerate the corrosion. The silicon, if applied liberally and over the entire surface, will keep moisture out. Just be careful, if not done thoroughly, you could make things worse: if the silicon is not covering 100%, then moisture will collect in any missed spots and the silicon could make it even more difficult for the moisture to dry out. Just go crazy with the stuff and let it ooze out everywhere as you reassemble, especially out through the screw holes. It will, in essence, form a gasket that will help project the areas of contact and the screw penetrations.

I would look for marine-grade sealant, just as an extra precaution (the kind that works on ocean-going boats under the waterline). That might actually not be silicon. I can't remember now, it might be some sort of polyester. You get the idea.
 
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Sorry, one more thought. Do you know the kind of metal used in the post? You should match the screws to that, otherwise you run the risk of a galvanic reaction between dissimilar metals that will exacerbate corrosion. Ideally the bracket, the screws and the post would be of the same metal, if possible.
 
Or that could all be overkill. Maybe those posts, as is, will outlast some other component of the system making these extra precautions pointless. Use your own judgement on that.
 
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